This invention relates to a method for detecting the presence of hydrocarbonaceous fuel and, more particularly, to a method for detecting the presence of hydrocarbonaceous fuel in the fuel inlet line to the cylinders of a fuel injection engine.
In fuel injection engines an air/fuel mixture is directed from an inlet line into the engine cylinders for combustion. It is desirable to be able to detect the presence and amount of fuel in the inlet line to the engine cylinders as part of the engine throttle control system so that efficient operation of the engine can be maintained. It is also desirable to be able to detect the amount of fuel being provided for combustion while the engine is on a production line engine test stand, so that efficient operation of the engine can be tested prior to the engine being installed in a vehicle.
A known prior art fuel detection system is the "hot wire" method of gas detection which examines the cooling effect of a fuel mist. This method involves heating a wire by running a constant current through it. A sample stream of fuel mist is directed across the wire. The voltage across the wie is measured to determine how much heat is removed from the wire by the sample stream. The greater the amount of heat removed by the sample stream, the greater the concentration of fuel mist in the stream.
Optical methods for detecting fuel mist have also been used in the prior art. These methods utilize an opacity meter for use with a sample stream containing exhaust from an operating engine. As the concentration of fuel particles in the exhaust increases, the transmission of light through the stream is reduced and light scattering is increased.
A problem associated with the prior art methods for fuel detection is that the systems are generally used solely as safety equipment and, consequently, do not have fast response or recovery times. Also the detection system, usually in the form of an alarm, must be reset after the presence of fuel or vapor is detected and the alarm is sounded. These methods have not been useful for testing continuously operating fuel injection engines or other equipment which utilizes fuel.